This invention relates to so-called rotationally molded doors. More particularly, a rotationally molded door is disclosed in which the hinge post is integrally attached to the skin of the rotationally molded door
In Johnson et al U.S. Pat. No. 5,693,271 entitled Rotationally Molding An Insulated Plastic Molded Door with Integral Hinge issued Dec. 2, 1997, there is disclosed a rotationally molded door of the type utilized in this disclosure. Simply stated, this patent disclosed a high impact resistant rotationally molded door and process for molding the door. In that disclosure, a hinge member is integrally molded to the door along one edge only. This hinge member forms to the hollow door edge without door warping during curing and shrinking of rotationally molded plastic door body. Door warping is avoided by delaying full integral attachment of the hinge member to the door until curing of the injected foam interior which both bonds to the interior of the door and the hinge member.
In Johnson et al U.S. Pat. No. 5,693,271, the hinge post extended from the top and bottom of the door. Due to expansion and contraction during the rotational molding process, it was desired not to attach the hard plastic skin of the door to the hinge post This enabled the respective ends of the hinge post to move with respect to the door skin after the molding was complete. Warping of the door from its planar disposition was avoided.
At the same time, it was necessary to key the hinge post to the door. Therefore, a tab was provided centrally of the hinge member. When the rotationally molded door was removed from the rotational mold, the molded door formed a hollow construction with the hinge post protruding through the hollow construction. This hollow construction was then injected with insulating and hardening foam. When the foam cured, it cured around the tab of the hinge post, holding the hinge post in place.
It is to be understood that the disclosed door is a heavy industrial type. As such, it includes a V-cam hinge, typically located and attached to the bottom comer of the hinge post. When the door is swung to the open position, the door rises on the hinge post against one side of the V-cam as the door swings to the open position. When the door is no longer held to the open position, the door falls on the hinge post against the V-cam and is biased to the closed position. It has been found in practice that this motion places considerable strain on the door hinge, and in particular on the attachment of the hinge post to the door. The result has been the occasional breaking of the union of the hinge post and door.
The reader will understand that this difficulty was only located after considerable experience. In so far as the prior art fails to teach this hinge post separation as a practical problem, at least partial invention is claimed in identifying the problem to be solved.
A high impact resistant rotationally molded door and process for molding the door has the hinge post integrally attached to the rotationally molded skin of the door. A hinge member is provided that has a perforate U-shaped metal sheet bonded to preferably the upper portion of the hinge post. The sides of the U-shaped metal sheet are spaced sufficiently apart so that registration with the subsequently rotationally molded plastic skin of the door occurs. This hinge member at the perforate metal sheet rapidly heats during rotational molding. The perforate metal thus bonds to integrally mold with the skin of the door. This bonding occurs as the hinge post is molded within the hollow door construction along its hinging edge. The hinge member attaches at the perforate U-shaped metal sheet to the skin of the door while all other portions of the hinge post are free to move with respect to the door. The door is thus formed without door warping during curing and shrinking of rotationally molded plastic door body. At the same time, when the door is in use, the perforate U-shaped metal sheet in its integral attachment to the rotationally molded skin of the door prevents dislodgment of the hinge post relative to the door.